1. Field of the Invention
The flexible suction pipe is installed through the bunghole in a tank and is positioned on the interior of the tank, with the inlet port of the suction pipe located at or near the bottom of the tank. In most circumstances, the flexible suction pipe connects to an adapter which is mounted in the bunghole of the tank. A pump is mounted on the exterior of the tank in fluid communication with the flexible suction pipe and the adapter. The flexible suction pipe allows the pump to withdraw substantially all of the fluid from the tank.
2. Description of the Prior Art
In the agricultural chemical business, tanks are typically manufactured using conventional rotational molding techniques from corrosion resistant thermoplastics such as high density polyethylene (HDPE). The position of the bottom of such tanks varies due to several factors. Those skilled in the art recognize that the tolerances of such tanks vary as much as plus or minus 1/2 inch, due to the limitations of rotational molding techniques and the physical properties of thermoplastics. When full of liquid, the bottom of the tank tends to flex outwardly approximately 1/2 inch. If mishandled, the bottom of a tank could be flexed inward by a forklift or other lifting means as much as 2 inches. Combining all of these factors together, the exact position of the bottom of the tank can vary approximately 21/2 inches up or approximately 1 inch down. Although this seems like a trifle, it is important in the design of suction pipes. [1/2" variance due to manufacturing tolerances (slightly undersize tank) +2" deflection due to mishandling =21/2" possible variance up]. [1/2" variance due to manufacturing tolerances (slightly oversize tank) +1/2" outward flex due to heavy fluid =1" possible variance down]. The term up, as used herein, means a movement of the bottom towards the interior of the tank; the term up is synonymous with the term inward. The term down, as used herein, means a movement of the bottom away from the interior of the tank; the term down is synonymous with the term outward.
The optimum design for a suction pipe dictates that the inlet of the suction pipe be located as close as possible to the bottom of a tank so that the pump can withdraw substantially all of the fluid from the tank. Unfortunately, the bottom of the tank is not always located an exact distance from the bunghole in the top of the tank. This complicates the design of suction pipes. Applicant believes that the actual position of the bottom of a tank typically used with agricultural chemicals can vary as much as 31/2 inches (21/2" up +1" down =31/2" possible variance). Because of these possible variances, the overall length of the suction pipe and the location of the inlet ar critical design considerations.
To accommodate for these variances, three different types of suction pipes have been developed for use in the agricultural chemical business. The first type of suction pipe is a rigid elongate one piece conduit which extends below the bung adapter into the tank. Because tanks come in various sizes, the length of the rigid conduit must vary. This leaves a manufacturer with two alternatives.
The first alternative is a standard length rigid one piece pipe designed to be located at or near the bottom of a tank per the specifications of the tank manufacturer. Unfortunately, the actual tank may vary somewhat from the specification. If the tank is a little small, the one piece suction pipe may not fit, so the manufacturer intentionally designs it to be a little short of the anticipated bottom of the tank. If the tank is mishandled, the bottom flexes inward and can hit the one piece rigid suction pipe causing it to snap off or shear at the bunghole adapter. If this happens, the entire system fails and the suction pipe must be replaced. To prevent a total failure of the system, the suction pipe designer makes the pipe even shorter. This minimum length suction pipe leaves a gap between the inlet of the suction pipe and the bottom of the tank. In tanks which are slightly oversize due to manufacturing variances, the gap is increased. When an oversize tank flexes downward, the gap is more pronounced. The larger the gap, the greater the amount of fluid that will be left in the tank.
The designer of a one piece rigid suction pipe is placed on the horns of a dilemma. Either a short design is chosen which seldom snaps off or an average length is chosen which has a greater probability of being snapped off due to compressive loading forces.
The other alternative for a rigid one piece design is to custom cut the length of each suction pipe for each separate tank. This is expensive and impractical for high volume, low cost production and can only address manufacturing variances. Tanks containing corrosive agricultural chemicals range in size from approximately 15 gallons to 160 gallons. When these tanks are full of fluid the weight of the fluid makes it necessary to use a forklift, chain hoist or some other mechanical means to move the tanks around. During the lifting process, the fork may be improperly placed causing approximately 2 inches of inward deformation of the bottom of a tank. Mishandling of tanks in this manner is a common cause of suction pipe failure, even if it is custom cut to length for that individual tank
The overall length of the present invention is flexible, due to the bellows construction, which allows the inlet of the suction pipe to be positioned at or near the bottom of the tank despite flexing, manufacturing variances, and mishandling. The present invention is much less prone to being snapped off or sheared when compared to a rigid one piece type suction pipe.
The second type of suction pipe commonly used with agricultural chemicals is a two piece telescoping apparatus, typically manufactured from two separate pieces of rigid plastic conduit having different diameters. Because the pump is placing negative pressure on the interior of the suction pipe, the two telescoping members have to fit tightly together or air will bypass through the annular gap. The telescoping suction pipe can be initially installed with the bottom telescoping member touching the bottom of the tank. If the tank is mishandled while being moved about, the overall length of the telescoping suction tube is shortened and the apparatus does not break. However, when the bottom of the tank flexes back down, there will be a gap between the inlet of the telescoping suction pipe and the bottom of the tank. This gap prevents the pump from fully emptying the tank. Obviously, the larger the gap the greater the amount of fluid that will be left in the tank. In the industry, telescoping suction pipes are generally thought to be an advancement over a rigid one piece suction pipe because they generally do not break off inside the tank. However, a telescoping suction pipe can only move in one direction. It can contract in overall length, but it cannot, without manual assistance, expand or return to its original length. The present invention is an improvement over the telescoping suction pipe because it can move in two directions without manual assistance due to the flexible bellows. This allows the inlet port of the flexible suction pipe to be located at or near the bottom of a tank at all times.
From the end user's point of view, it is desirable to remove as much fluid from the interior of the tank as practically possible. In some circumstances, a farmer will go to an agricultural chemical dealer and will purchase, for example, sixty gallons of a concentrated agricultural chemical. The plastic tank, the suction pipe, and the pump are owned by the agricultural chemical dealer and are merely loaned to the farmer. The farmer picks up the tank and takes it to his field to transfer the chemical to a tractor o other implement for application to his field or crops. When the tank is empty, the farmer returns the tank, pump and suction pipe to the agricultural chemical dealer for reuse by others. If there are two or three gallons of the chemical sloshing around in the bottom of the tank that the farmer cannot pump out, he feels that he has paid for a product which was not delivered. The cost of concentrated agricultural chemicals can range from $10.00 to $300.00 per gallon (1991 prices). It is therefore important from the farmer's point of view to be able to substantially empty the tank.
If the farmer attempts to obtain a refund for the chemical which is left in the bottom of the tank, there is always a question as to exactly how much chemical is sloshing around inside. Furthermore, a refund situation creates more paper work and hassle for the parties. It is therefore highly desirable to design a suction pipe which will, to the extent practically possible, empty the tank.
The third type of suction pipe used in the agricultural chemical industry is a multi-piece spring loaded telescoping suction pipe which allows the bottom of the suction pipe to travel up and down during movement of the bottom of the tank and to adjust its length for manufacturing variances in tank size The spring in the apparatus causes the bottom of the suction pipe to be urged into contact or near proximity with the bottom of the tank, to the limit of the mechanical stroke of the telescoping member. The spring loaded suction pipe attempts to eliminate or at least minimize the ga between the bottom of the suction pipe and the bottom of the tank. These spring loaded telescoping suction pipes are relatively expensive to manufacture because of the multi-piece construction. The metal spring is exposed to corrosive agricultural chemicals. In most cases, these spring loaded telescoping suction pipes have a short stroke which is insufficient to always maintain contact with the bottom of the tank. For example, the total stoke (from full up to full down) of the Science multi-piece spring loaded telescoping suction pipe is believed to be less than 11/2 inches. Applicant believes that the total movement in the bottom of a tank can be as much as 31/2 inches up and down, as discussed above.
There has been a long felt need in the agricultural chemical business to develop an inexpensive suction pipe which stays on the bottom of the tank, is resistant to being snapped off and which does not contain corrosive components.
Several prior art patents, including U.S. Pat. No. 3,017,898 and No. 4,510,968 disclose a conical bellows for use with a multi-piece suction pipe as discussed in the Information Disclosure Statement filed concurrently herewith.